Floppy disk variants
The floppy disk is a data storage and transfer medium that was ubiquitous from the mid-1970s well into the 2000s.In addition to the four generations of floppy disks there were many other floppy disk developed, either using a different disk design or special layout and encoding methods for the data held on the disk. Some with limited adoption were failed attempts to establish a standard for a next generation.
Non-standard media and devices
Burroughs 8-inch Drive and Media
From 1976 until 1984 Burroughs offered a line of two sided 8-inch floppy disks and drives on its systems, initially at 1.0 MB and then at 3.0 MB. They were not compatible with the then industry standard 8-inch disk or drive. The 3.0 MB version used a servomechanism to achieve its higher-capacity.IBM DemiDiskette
In the early 1980s, IBM Rochester developed a 4-inch floppy disk drive, the Model 341 and an associated diskette, the DemiDiskette. At about half the size of the original 8-inch floppy disk the name derived from the prefix demi for "half". This program was driven by aggressive cost goals, but missed the pulse of the industry. The prospective users, both inside and outside IBM, preferred standardization to what by release time were small cost reductions, and were unwilling to retool packaging, interface chips and applications for a proprietary design. The product was announced and withdrawn in 1983 with only a few units shipped. IBM wrote off several hundred million dollars of development and manufacturing facility.Tabor Drivette
Another unsuccessful diskette variant was the Drivette, a 3¼-inch diskette drive marketed by Tabor Corporation of Westland, Massachusetts, USA between 1983 and 1985 with media supplied by Dysan, Brown and 3M. The diskettes were named Dysan 3¼" Flex Diskette, Tabor 3¼" Flex Diskette, sometimes also nicknamed "Tabor" or "Brown" at tradeshows. The Microfloppy Disk Drive TC 500 was a single-sided quad-density drive with a nominal storage capacity of 500 KB. It could work with standard controllers for 5¼-inch floppy disks. Since August 1984, it was used in the Seequa Chameleon 325, an early CP/M-80 & MS-DOS portable computer with both Z80 and 8088 processors. It was also offered in limited quantity with some PDP-11/23-based workstations by General Scientific Corporation. Originally, Educational Microcomputer Systems announced a system using this drive as well, but later changed plans to use 3½-inch diskette drives instead.3-inch "MCD-1 Micro Cassette"
A magnetic disk in a hard plastic shell was invented by, who was working at the Hungarian Budapest Radio Technology Factory, in 1973. In 1982, such a product, the 3-inch MCD-1 was announced internationally and Jack Tramiel showed interest in using the technology in his Commodore computers, but negotiations fell through. Versions of the floppy drive were released in minimal quantity for the ZX Spectrum and Commodore 64, and some computers made in East Germany were also equipped with one. The floppies are single sided and can hold up to 149 KB of data when MFM formatted. The drives were compatible with contemporary floppy controllers. Production was very limited in the early 1980s due to manufacturing problems and the product was abandoned by 1984 after the industry adopted a standard 3.5 inch format.3-inch "Compact Floppy Disk" / "CF-2" format
The 3-inch "Compact Floppy Disk" or "CF-2" was an intended rival to Sony's 3.5" floppy system introduced by a consortium of manufacturers led by Matsushita. Hitachi was a manufacturer of 3-inch disk drives, and stated in advertisements, "It's clear that the 3" floppy will become the new standard."The format was widely used by Amstrad in their CPC and PCW computers, and the Sinclair ZX Spectrum +3. It was also adopted by some first-party manufacturers/systems such as Sega, Yamaha, the Oric, the Tatung Einstein, and Timex of Portugal in the FDD and FDD-3000 disk drives and a number of third-party vendors such as Amdek, AMS, and Cumana who provided drives for use with the Apple II, Atari 8-bit computers, BBC Micro, and TRS-80 Color Computer. Despite this, the format was not a major success.
Three-inch diskettes bear much similarity to the -inch size, but with some unique features. One example is the more elongated plastic casing, taller than a -inch disk, but less wide and thicker. The actual 3-inch magnetic-coated disk occupies less than 50% of the space inside the casing, the rest being used by the complex protection and sealing mechanisms implemented on the disks, which thus are largely responsible for the thickness, length, and relatively high costs of the disks. On the early Amstrad machines, the disks are typically flipped over to change the side as opposed to being contiguously double-sided. Double-sided mechanisms were introduced on the later PCW 8512 and PCW 9512, thus removing the need to remove, flip, and then reinsert the disk.
Quick Disk variants
marketed several 3-inch diskette "Quick Disk" formats for OEM use. They used 2.8-inch magnetic discs. The OEM could decide on the outer case of the media which led to several mechanically incompatible solutions:Famicom Disk System
The Japanese Nintendo Famicom Disk System used proprietary 3-inch diskettes called "Disk Cards" between 1986 and 1990, based on Mitsumi's Quick Disk media.Smith Corona DataDisk
Many Smith Corona "CoronaPrint" word-processor typewriters used a proprietary double-sided 3-inch diskette format named "DataDisk". Confusingly, it was labelled 2.8-inch reflecting the diameter of the magnetic disk itself rather than the media's case.Sharp 2.5-inch floppy disk
In 1986, Sharp introduced a 2.5-inch floppy disk format for use with their family of BASIC pocket computers. Two drives were produced: the Sharp CE-1600F and the CE-140F. Both took turnable diskettes named CE-1650F with a total capacity of 2×64 KB at bytes per side, 48 tpi, 250 kbit/s, 270 rpm with GCR .2-inch floppy disks
At least two incompatible floppy disks measuring two inches appeared in the 1980s.One of these, officially referred to as a Video Floppy can be used to store video information for still video cameras such as the original Sony Mavica and the Ion and Xapshot cameras from Canon. VF is not a digital data format; each track on the disk stores one video field in the analog interlaced composite video format in either the North American NTSC or European PAL standard. This yields a capacity of 25 images per disk in frame mode and 50 in field mode.
Another 2-inch format, the LT-1, is digitally formatted—720 kB, 245 TPI, 80 tracks/side, double-sided, double-density. They are used exclusively in the Zenith MinisPORT laptop computer circa 1989. Although the media exhibited nearly identical performance to the 3½-inch disks of the time, they were not very successful. This was due in part to the scarcity of other devices using this drive making it impractical for software transfer, and high media cost which was much more than 3½-inch and 5¼-inch disks of the time.
Much later, another 2-inch miniature disk format was Iomega's PocketZip, introduced in 1999. The disks could store 40 MB. The external drives were available as PC Card Type II and with USB interface.
Extended use cases
Flippy disks
A flippy disk is a double-sided -inch floppy disk, specially modified so that the two sides can be used independently in single-sided drives. Many commercial publishers of computer software distributed their products on flippy disks formatted for two different brands of computer, e.g. TRS-80 on one side and Apple on the other. Compute! published an article on the topic in March 1981.Generally, there are two levels of modifications:
- For Disk Operating Systems that do not use the index hole in the disk to mark the beginnings of tracks, the "flippy" modification required only a new write-enable notch to be cut if the disk was designed to be written to. For this purpose, specially designed single-rectangular-hole punchers, commonly known as disk doublers, were produced and sold by third-party computer accessory manufacturers. Many users, however, made do with a standard hole puncher and/or an ordinary pair of scissors for this job.Image:Spiderman_Flippy_Disk.jpg|right|thumb|Commercial nonwriteable Flippy disk with no write notches and two jacket index windows
- For disk operating systems that do use index sync, a second index hole window has to be punched in both sides of the jacket, and for hard-sectored formats, an additional window must be punched for the sector holes. While cutting a second notch is relatively safe, cutting an additional window into the jacket is a great peril to the disk itself.